I have a 1988 90 Quattro and little or no heat comes from the vents. I recently replaced the water pump and thermostat because of an overheating condition. I did have heat before that. I tried to bleed the air out using the bleeder that is in the heater hose at the firewall. I get semi-warm air. But the next day it is cold again. It does not seem to have a heater valve.
My question is: What is the proper procedure for bleeding the cooling system on that car ?

 

I just let it leak as I add coolant into the reservuar. I heat up the car to about 70C and I rev very high till like 4000-5000RPM for couple of seconds, and thats all.

 

check for a screw on top of the radiator ,,, if you got one then thats where the bleeding should take place .... if you dont have one there than heat up the car (let it run till temp rises) and open up the reservuor cap to let of some pressure

 

Provided that I have bled all air from cooling system. Both heater hoses seem to be hot. Vents still blow semi warm air. Temp gauge reads low. Is there a door or flap that may prevent air flow through the heater core and into the cabin? Is it vacuum operated? How do I get to it without the use of a saws all? It is getting too cold in New England for no heat.

 

when u do run the car, and there is warm air coming out, and the car is warmed up. first check that the tubes of the heater core are hot. if they are warm, then rev the engine couple of times high. and u should experience burst of hot air, if not. u probably have a clog in the system. if the tubes are hot, then u probably broke the cable, that turns a door for the heater core.

 

My cooling system loses coolant in time. It looks like it evaporate somewhere. Audi 100 td 87.
Is there some aditive that can fix those small holes?

 

don't put additives in your cooling sys ... find the leak and fix it

 

if you cant find leak in the engine bay, then there is a chance for the leak to be in the heater core.
if you use stop leak stuff, it will clog the rad.

 

According to bentley, to blead the system unscrew the bleeder valve on the heater hose approx. 2 full turns and the bleeder valve on the coolant pipe on the back side of the engine. the second valve is located just behind the driver's side bank on the coolant pipe next to the cps.

 

People, friends, buddies, help! I have a problem. Under the cap of expansion tank there is abundant bleeding of coolant when the engine reaches about 90C and further. Some say it's about thermostat. Is that so? If it is, which thermo to buy. And, btw what is normal summer temperature of turbo diesel engine?